PROBLEM RESOLVED
To get ESX to install successfully on my Precision 370 I did the following;
#1 To bypass the initial "CPUID" error as above;
1. At the initial bootloader screen (when booting from the ISO), press TAB to edit the boot options
2. Hold down the left-arrow key to move the cursor back to the beginning of the boot options, and add "nocheckCPUIDLimit" right after "vmkernel.gz", so that the first part of the boot options BEFORE the first "---" reads: "mboot.c32 vmkernel.gz nocheckCPUIDLimit ---"
3. Press ENTER.
(thanks to Dave Mishchenko for posting the fix -
http://communities.vmware.com/thread/159556?tstart=15)

#2 To allow the installer to recognise/install onto the internal SATA disk
In the BIOS (Drives | SATA Operation), changed config from Combination (SATA/PATA mode) to RAID Autodetect/ATA (RAID if signed drives, otherwise ATA)

Hope this helps someone else who like me is also looking to play with ESX without purchasing supported hardware.
PS Apologies for posting under a different login but couldn't my original credentials.

Update to above;

Despite successfully installing ESX on a Precision 370 the kernel still failed to initialize at startup (same CPUID value error as above)... to overcome here's what I did;

During initialization of the kernel, I pressed SHIFT+O (allows advanced options to be specified during boot), typed 'nocheckCPUIDLimit' (without quotes), then hit ENTER to continue - this allowed me to run ESX and successfully create a VM. Hope that makes sense.

Now if only I can find how to make 'nocheckCPUIDLimit' a persistent option... I understand this can be achieved through modding the esx.conf file, but I haven't figured out how to do this yet... any ideas would be much appreciated.

Thanks in advance,

I had to make a couple changes for ESXi 4.0

To get ESX to install successfully on my Precision 370 I did the following;

#1 To bypass the initial "CPUID" error as above;

1. At the initial bootloader screen (when booting from the ISO), press TAB to edit the boot options
2. Hold down the left-arrow key to move the cursor back to the
beginning of the boot options, and add

mboot.c32 vmkboot.gz nocheckCPUIDLimit --- vmkernel.gz nocheckCPUIDLimit ........

3. Press ENTER.

#2 To allow the installer to recognise/install onto the internal SATA disk
In the BIOS (Drives | SATA Operation), changed config from Combination
(SATA/PATA mode) to RAID Autodetect/ATA (RAID if signed drives,
otherwise ATA)

On Reboot

Hold SHIFT+O at boot screen and enter nocheckCPUIDLimit as a kernel parameter

Using vClient

Enter Maintenance Mode

Configuration > Software > Advanced Settings > VMKernel > Disable checkCPUIDLimit

After that everything worked great !

Why you don't youse VM Workstation and install the ESXi in it?